The invention relates to a method for working or forming a workpiece by flow-forming, particularly for the manufacture of internal teeth on the workpiece, in which a cup-shaped preform or blank is axially fixed against a tool chuck and pressed by means of at least one rolling member onto the tool chuck and the blank is rotated relative to the rolling member.
Numerous different methods are used in the non-cutting manufacture of internal teeth by flow-forming. Thus, DE 196 36 567 A1 (cf. FIG. 4) describes a manufacturing method called climb-stretching. In the climb-stretching manufacturing method, a blank is radially centered and fixed by an axial pressure against the tool chuck. The feed movement of the spinning rollers takes place from the tailstock side, so that the spinning rollers set to the external diameter of the workpiece reduce the external diameter of the blank and press the material into the profile on the circumference of the tool chuck and thereby roll it out in the axial direction.
DE 196 36 567 A1 (cf. FIG. 5) describes the manufacture of internal teeth by radial rolling in. The blank is radially centered and axially fixed on the base side, so that in the case of a radial infeeding of the spinning rollers the displaced material radially and axially penetrates the profile of the tool chuck.
In another method variant (cf. DE 196 36 567 A1, FIG. 6), the preform or blank is radially centered and axially fixed on both sides, so that on a radial infeeding of the spinning rollers, the displaced material penetrates and fills the tool chuck profile.
Finally, in the case of a climb-stretching with axial stop member (cf. DE 196 36 567 A1, FIG. 7), the blank is radially centered and axially fixed on the base side of the blank. In the axial direction, the tool chuck carries a stop member against which the material flows during flow-forming and which stops the material as soon as, through the feed movement, the spinning rollers, set to an external diameter of the workpiece, are moved from the tailstock side against the blank and displace the material. In this method, the material can only penetrate in the radial direction into the tool chuck profile and can increase in diameter against the frictional resistance of a stop member face.
In all these methods the radial bulging problem arises, being caused by the mutual spacing of the spinning rollers, which occurs due to the geometrical dimensions of the spinning rollers with their bearings. The consequence is a reversed loading in the tool chuck profiles during working or forming.
It is also common to all these methods that at the start of forming, the radial resistance of the material, from the ring-shaped transition area between the base and wall of the blank, must be overcome. To this, must be added the support of the wall of the blank on the toothed crests of the tool chuck. Thus, varying forming forces due to the different resistance during the forming of the blank lead to different workhardnesses within the shaped profiles in the workpiece. As constant forming forces are a prerequisite for constant tolerance ranges on the workpiece profile, a fluctuating tolerance range must be expected. This is a method-caused, serious disadvantage during the manufacture of workpieces requiring precise dimensioning in accordance with the aforementioned methods.